<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #d1{
            color: red;
            font-size: 15px;
            font-weight: bold;
            background-color: aqua;
            border-radius: 8px;
        }
        #d1-1{
            border: solid 1px red;
        }
        #d1-1-1{
            border: solid 1px blue;
        }
    </style>
</head>
<body>
    <div id="d1">祖先
        <div id="d1-1">父
            <div id="d1-1-1">子</div>
        </div>
    </div>
</body>
</html>